Patent Literatures (PTLs) 1 to 4 disclose methods of broadcasting or multicasting in a virtual network. Patent Literature 1 discloses a method of assigning an address of a carrier virtual Local Area Network (CVLAN) for a layer 2 network (below, “L2NW”) for each physical port and VLAN, and assigning a broadcast or multicast address to each CVLAN, to realize broadcasting/multicasting.
In Patent Literature 2 there is provided a virtual hub that learns and stores relationships between a source MAC address inside a user MAC header in a received packet, and a terminal-side virtual interface through which the packet passes; and there is a disclosure of a packet routing method that uses an access router, which forwards the packet based on this stored information, and, on a network side, adds a VPN number, performs encapsulation in an IP packet and carries out transmission. In the same literature, broadcasting is realized by setting up a server for broadcasting, known as a packet copy server, and copying and forwarding to another access router within the same VPN (refer to paragraph 0122, seventh exemplary embodiment).
Patent Literature 3 discloses a node that adds an extension tag including forwarding information to a node on an exit side, to an input data frame, and performs forwarding. There is a description that when performing broadcasting, by setting forwarding information of a node on an input side (for example, a source MAC address) in the extension tag, data frames are relayed (claim 3, paragraphs 0129 and 0137).
Patent Literature 4 discloses a method of switching a packet by a transmission medium provided with a plurality of terminals connected using different links. The same literature has a description of preventing packet loops, by using an identifier list (broadcast control information) linked 1-to-1 with a switch through which frames pass (paragraphs 0038 to 0040).
Non-Patent Literatures (NPLs) 1 and 2 disclose a network in which communication is taken as end-to-end flow, and which includes switches called “OpenFlow switches” that process flows thereof, and a controller that sets control information known as “flow entries” for the switches.
PTL 1:
    Japanese Patent Kokai Publication No. JP2000-286853APTL 2:    Japanese Patent Kokai Publication No. JP2002-247089APTL 3:    Japanese Patent Kokai Publication No. JP2004-266874APTL 4:    Japanese Patent Kohyo Publication No. 2007-534191ANPL 1:    Nick McKeown et al., “OpenFlow: Enabling Innovation in Campus Networks,” [online], [search carried out on Mar. 14, 2012], Internet <URL: http://www.openflow.org/documents/openflow-wp-latest.pdf>.NPL 2:    “OpenFlow Switch Specification, Version 1.0.0. Implemented (Wire Protocol 0x02),” [online], [search carried out on Mar. 14, 2012], Internet <URL:http.//www.openflow.org/documents/openflow-spec-v1.1.0.pdf>.